Cha-cha's dress was a thrift store dress that got a "shelf" bust line made of the hem cut off of one of the longer prom dresses when we shortened it. We glued Dollar Tree carnations to a piece of felt and then sewed them on (always trying to ensure the dresses can be used again for other things!)
Our "Jan" wore padding to make her very curvy. To hide her bra straps we added lots of chiffon at the top and to emphasize her waist we added chiffon at the middle. This was another thrift store dress.
Prom dresses that looked like they came from the 50s were hard to find. We did a lot of shortening of thrift store finds (mainly bridesmaid dresses) and added crinolines underneath to give the skirts some fullness. Some, like this one came with crinoline built in. Had to add straps because of the dancing--didn't want anyone to get flashed!
Poodle skirts were handmade from a circle skirt pattern. The waistband was from blanket binding which acted as the channel for the elastic. Since more than one character wore the skirts, we had to keep them as flexibly sized as possible. The designs were hot-glued on.